Peel onions and garlic. Chop the onions finely, chop the garlic. Bring the stock to the boil. Heat butter in a pot, fry half of the onions and garlic in it until transparent. Add rice and fry until transparent, stirring continuously. Add white wine and let it simmer. Add some hot broth until the rice is covered and simmer until the rice has absorbed the broth. Add the hot stock again and again and let it simmer openly at low to medium heat until the risotto is creamy (25-30 minutes). Stir in between
Clean, wash and drain the zucchini, peppers and tomatoes. Dice the vegetables. Wash sage, shake dry and chop the leaves. Heat the oil in a pan and sauté the remaining onions and garlic, as well as the peppers, zucchini and sage for 4-5 minutes. Add tomatoes, season with salt and pepper and braise covered for about 5 minutes. Season the finished ratatouille with salt and pepper
Stir 50 g parmesan and mascarpone into the finished risotto, season with salt and pepper. Place the risotto in a greased ovenproof dish and spread the ratatouille vegetables on top. Sprinkle with 25 g parmesan and bake in a preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for approx. 5 minutes. Garnish with parsley as desired